This invention relates to protonated lignin-polyamines, quaternary ammonium salts of lignin polyamines and sodium-, potassium-, salts of lignin polyamines.
The objective of this invention is to provide new improved lignin amines, which are characterized by high nitrogen content and are water soluble at both alkaline and acidic pH values. In addition, a wide variety of applications for these products is described.
The most widely applicable method to introduce a nitrogen functionality into lignin is by the Mannich Reaction, which involves condensation of ammonia, primary or secondary amine and a suitable aldehyde onto the unsubstituted position ortho to the phenolic hydroxyl group. The manufacture of amines from kraft lignin by this method is disclosed in U.S. Pat. No. 2,863,780 by J. C. Ball and U.S. Pat. No. 2,709,696 by E. G. Wiest. Kraft lignin is obtained from the spent lignin of the kraft pulping process by acidification. This lignin is insoluble in water at pH values from 1 to 7 and soluble at pH values of 8 and above. The preparation of aminoalkylated lignin prepared from hydroxyphenylated lignosulfonate is disclosed in U.S. Pat. No. 4,017,475 by C. H. Ludwig. Lignosulfonates are isolated from spent sulfite liquors, a by-product of the sulfite pulping process. Dihydro-oxazine derivatives of kraft lignin obtained by reaction of kraft lignin with methyl amine and formaldehyde are disclosed in Canadian Pat. No. 1,018,520 by A. B. McKague, quaternary ammonium salts based on aminomethylated lignins are disclosed in U.S. Pat. No. 3,407,188 by G. A. Cavagna, and Canadian Pat. No. 1,018,519 by A. B. McKague. A variety of kraft and sulfite lignins containing quaternary ammonium-functionalities are disclosed in U.S. Pat. Nos. 3,470,148 and 3,600,308 by G. G. Allan and in U.S. Pat. Nos. 3,857,830 and 3,935,101 by W. S. Briggs.
In the recent U.S. Pat. No. 4,455,257 by H. W. Hoftiezer, et al., the "cationic" reaction products of kraft lignin with aldehyde and polyamine are disclosed. These products and the above described Mannich-lignin amines are useful as flocculating agents for clay and other finely divided materials. However, the reaction products of lignin, formaldehyde and polyamines, as described in U.S. Pat. No. 4,455,257, in fact, are not soluble at acidic pH values and they are also not in solution when they are prepared at alkaline pH values.